Transformer system



Aug. 15, 1950 A. E. FEINBERG,

TRANSFORMER SYSTE Filed` umn s, 1947 INVENTOR.

Albert E. Feinberg By A Homey Patented Aug. ,-15, 1950 UNITED STATESPATENT OFFICE t f 2,518,814 I 'mwst-oma SYSTEM poration ot Illinoisapplicati@ Mann s, 1w, serial No. 731,991 s claims. (ci. 32a- 451) Thisinvention relates to transformers, and more particularly to atransformerV for operating a plurality of hot cathode glow dischargetubes, such as fluorescent tube lamps.

In order to improve the power factor of lighting circuits in fluorescenttube lamps, and for other desirable purposes, it hasbeen customary tooperate the tubes in pairs off of a single transformer. The transformerhas a primary winding and a pair of secondaries, one for eachfluorescent tube, the secondaries being connected in step-up autotransformer relationship with the primary. A condenser is provided inseries with only one of the tubes and of sufficient capacity to causethat tube to draw a leading current to compensate for the laggingcurrent taken by the other tube. Y

Fluorescent lamps of the hot cathode type are started by providing atemporary series connection between the filaments at the opposite endsof the tube. In starting two lamps which are operated from a singletransformer in a circuit as above set forth it has been found that thecondenser in series with one ofthe lamps in many instances reduces thecurrent flowing to that lamp to an undesirable amount. In addition, inmany instances there is sufiicient intercoupling within the secondarycoils of the transformer so that a reduction of thecurrent flowing inthat secondary `which is in series with the condenser results in anincrease of the current flowing in the other secondary which isconnected to the other lamp. Thus the condenser not only diminishes theamount of current flowing to one of the lamps but frequently alsoincreases the amount of current flowing to the other lamp, both changesbeing to undesirable degrees. The resulting voltages across the lampsare also changed.

Itis one of the objects of the present invention to provide an improvedtransformer structure and circuit arrangement wherein the current -waveof the leading lamp issubstantially sinusoidal, thereby eliminating thethird harmonic which is otherwise frequently present in the wave form.It is a further object of the present invention to provide a transformerofthe above mentioned character wherein the circuit arrangement is suchas to permit a much lower saturation of the iron core and therefore acorrespondingly lower maximum temperature rise in the iron. Itis a stillfurther object of the present invention to provide a circuit'arrangement wherein the secondary requires a lower flux density therebypermitting a diminution in thev to the drawings wherein like referencenumeralsv designate like parts throughout.

In Figure l there is shown a transformer I comprising an iron coreformed of a stack'of L- shaped laminations assembled through six similar(but not identical) coils. Each lamination includes a longr leg 2 and ashort leg 3, the laminations being assembled so that the abutment 4between adjacent laminations in the same layer are at theloppositecorners of a rectangle, and with the abutments 4 of adjacent layersstaggered at opposite sets of corners of the rectangle. The transformerof Figure 1 includes a pair of series connectedprimary coils 6 and l, apair of series connected secondary coils 8 and 9 which will ultimatelysupply the leading current, and another pair of series connectedsecondary coils I0 and Il which will ultimately supply the laggingcurrent. The two coils 6 and I will hereinafter be referred to as theprimary, the two coils 8 and 9 will hereinafter be referred to asazsecondary and the two coils I0 and II will hereinafter be referred toas another secondary. Each secondary is connected in step-up autotransformer relationship to the primary. The secondary I0-II isconnected through a lead I5 to one side of a filament I6 of a hotcathode glow discharge tube I 8, of the fluorescent type. The other sideof the filament I6 is connected through a starter I9 to one side of afilament 20 of the lamp Il. The other side of the filament 20 isconnected to one line of the source of power 2|. The secondary B-S isconnected through a lead 25 to the winding 26 of an iron core reactancefrom which the circuit is extended through a condenser 21 to one side ofa filament 28 of the leading lamp 2S, which is also of the hot cathodeglow discharge type. preferably a fluorescent lamp. The other side ofthe filament 2l is connected to a starter 30, preferably, although notnecessarily. in series with a compensating winding 3| and then connectedto the opposite filament 3i of the dred sixty turns.

former.

lamp 29, that illament being also connected to the line 2|.

In the construction herein shown the primary coils 6-1 are located asclose as possible to the secondary coils 8 and 9 and as far as possiblefrom the secondary coils I and In one preferred construction involving atransformer for use on a 118 volt 60 cycle line with two tubes each of40 watts,` each of the primary coils was two inches long and containednine hundred turns. Each of the secondary coils was one andninesixteenths inches long and contained seven hun- The coil 26contained five hundred turns and the compensating winding 3| containedthree hundred fty turns. The windings 2|A and 3| were connected incumulative series during starting to constitute a step-up trans- Whenthe starting switch opens its circuit the compensating winding 3| is, ofcourse, open circuited.

In the circuit of Figure 1 the secondary |0| is loosely coupled with theprimary so that there is sufficient leakage reactance to limit thecurrent flowing to the lamp |8, during starting, to its correctoperating value. being close to the primary has insufficient leakagereactancev to supplythe proper operating current to the lamp 29 whenused in series with the condenser 21 which is of a size such that thecapacitative reactance of the condenser is substantially greater thanthe inductive reactance of the windings 8-9. The reactor 26 is of such avalue that during operation the sum of the reactance 26 plus thereactance of the coils 8-9, in relation to the capacity reactance 21, isof the correct value in relation to the open circuit voltage and lampimpedance to supply the proper operating current to the lamp. The effectof the reactance 26 is to correct the crest factor of the current in thelamp 29 to a much lower value than can be obtained without it.

As a result of the circuit arrangement shown in Figure 1 the currentwave form of the leading lamp 29 is essentially sinusoidal, and the wattoutput of that lamp is raised thereby permitting a decrease in thecurrent flowing therethrough. The elimination of the third harmonic inthe wave form and the reduction of the leakage reactance of thesecondary 8-9 results in a much lower saturation of the iron core andcorrespondingly amuch lower temperature rise in the iron. Furthermore,due to the v,lower ux density required in the coils 8-9 it has beenfound possible to reduce considerably the number of turns in the othercoils on the core, resulting in a still further decrease in heating anda saving in copper. The

compensating winding 3| may be wound on thev same iron core as carriesthe winding 26, or the compensating winding 3| may be on a differentiron core.

The effect of the reactance 26 during starting is substantially greaterthan it is during operation, by reasonof the fact that during startingthe compensating winding 3| is in the circuit whereas during operationthe compensating winding 3| is not in the circuit.

The transformer and the reactances 26 and 3| and the condenser 21 areall located in a single container or can from which extend the variousconnecting leads for the external circuit. This includes the leads thatconnect to the line 2|,

the lead |5, the two leads from the reactance 3|,'

and the lead from the condenser 21 that is to be connected to the lament28. By this arrangement the circuit connections to the two lamps I8 Thesecondary 8-9 4 and 29 can be made as shown, whereby the reactance 3|may selectively be connected in circuit or disconnected from thecircuit, depending upon whether or not the starter switch 30 is closed,or open.

In Figure 2 I have shown a circuit arrangement substantially the sare asthat in Figure 1, differing therefrom only in that the positions of thecoils 1 and 9 have been interchanged. In other respects the two circuitsare the same.

In compliance with the requirements Yof the patent statutes I have hereshown and described a few preferred embodiments of my invention. Itishowever, to be understood that the invention is not limited to theprecise constructions here shown, the same being merely illustrative ofthe principles of the invention. What I consider new and desire tosecure by Letters Patent 1. Apparatus for supplying a plurality ofseparatly operable hot cathode glow discharge devices with leading andlagging currents respectively comprising an elongated core, a primarypositioned on said core intermediate the ends thereof, a pair ofsecondaries positioned on the core one at each end thereof, each of thesecondaries being connected to the primary to form a ste -up autotransformer, the primary being subs ntially closer to one of thesecondaries than to the other secondary, a condenser in series with thesecondary that is closest to the primary, and a two coil inductance withthe coils thereof inductively coupled together and separate leadsextending from the respective coils of the two coilzinductance to permitselective connection of one or both of the two coils of the inductancein series .with one another and with the secondary coil that is closestto the primary.

2. Apparatus for operating two hot cathode discharge tube loads,comprising a transformer having a two coil primary winding, a leadingsecondary winding having two coils, a lagging secondary winding havingtwo coils spaced from the primary and less closely coupled thereto thanis the rst secondary, a core for said windings, said core being of anelongated rectangular shape one coil of each of the three windings beingon one longitudinal side of the core and the other coil of each windingbeing on the other longitudinal side of the core, leads from therespective secondaries for individual connection to different tubecircuits, a condenser in the circuit of the lead from the leadingsecondary, and a two coil reactor having an iron core separate from theaforementioned rectangular core and magnetically coupling the coils ofthe reactor, one of the reactor coils being connected in series circuitwith the condenser and the leading secondary and the other reactor coilhaving conductor leads therefrom for permitting the selective connectionthereof into said series circuit during starting of the tubes and out ofsaid series circuit during operation of the tubes, so that the value ofthe reactance may be changed as the associated tube changes fromstarting condition to operating condition.

3.' Apparatus for operating two hot cathode discharge tube loadscomprising a transformer having a primary, a fu'st secondary, a secondsecondary spaced from the primary and less closely coupled thereto thanis the first mentioned secondary, both secondaries being electricallyconnected to the primary in step-up autof 5 tudinai sides joined tyondaries and said primary each comprising two series connected coils oneon each of the two opposite longitudinally extending sides of the core,leads from the respective secondaries for indi- ;'vidual connection todifferent tube circuits, a

reactor coil and a condenser in series and connected in series with alead from the rst secondary, said reactor coil having an iron core andbeing outside of the magnetic circuit of the tionship, said transformerhaving a rectangular core including opposite longitudinal sides joinedby transverse ends, said secondaries and said primary each comprisingtwo series connected coils one on each of the two oppositelongitudinally extending sides of the core, leads from the re-V spectivesecondaries for individual connection to dierent tube circuits, areactor coil and a condenser in series and connected in series with alead Afrom the iirst secondary, said reactor coil transverse ends, saidsechaving an iron core and being outside of the magnetic circuit of thetransformer, an additional coil on said last mentioned iron core andmagnetically coupled to the reactor coil, a starter switch in thecircuit of the leading tube with the condenser, and circuit connectionsincluding said switch and said additional coil in circuit between theheating laments of said last mentioned tube and open circuiting saidadditional coil upon opening of the starting circuit of said lastmentioned tube.

5. Apparatus such as defined in claim 2 wherein the two primary coilsand the two leading secondary coils are adjacent one another and withone of the primary coils adjacent an end of one longitudinal side of thetransformer core and one leading secondary coil adjacent thecorresponding end of the other longitudinal side of the transformercore.

ALBERT E. FEINBERG.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Y Date

